A person can feel more alone than ever even with a live-in relationship. I felt that way in my last marriage, it’s even more crushing and soul wrenching than actually being alone in solo polyamory. Remembering how I felt during that time in my life keeps everything in perspective for me when I get lonely now. When I ended my marriage, I realized that there wasn’t a single moment I actually missed my ex-husband. Sure I may have missed things we did together, or maybe parts of the carefree lifestyle I had lived, but I didn’t miss him. I believe that feeling lonely or missing someone you love is a reminder that partner means something to us. That’s how I knew my marriage was at its end.
If we didn’t have sadness or loneliness, we would not feel elation from “happiness high” you describe. I believe in duality, akin to yin and yang in Chinese philosophy, that every moment alone makes us grateful for the amazing moments we do spend with the people we love. ❤